Epidemic of infectious diseases is a common and frequently-occurring disease caused by pathogens such as bacteria and viruses. It can spread among people and cause epidemics. In the old society, due to the epidemic of plague, cholera, smallpox, schistosomiasis, typhoid fever and other infectious diseases, our people were poor and sick, with an average life expectancy of only 35 years. After liberation, the party and the government attached great importance to the prevention and treatment of infectious diseases, and some serious infectious diseases have disappeared in China. On September 1989 and 1, China promulgated the Law on the Prevention and Control of Infectious Diseases in People's Republic of China (PRC), which effectively controlled many infectious diseases. However, at present, the incidence rate of infectious diseases in China still accounts for the first place in the total annual incidence rate, and there is still a long way to go to popularize the knowledge of infectious diseases prevention and enhance the public's awareness of disease prevention and finally eliminate infectious diseases. Summer and autumn are the high incidence seasons of gastrointestinal infectious diseases. Therefore, starting from this issue, we will continue to publish the common sense of infection prevention and control in the column of medical common sense.
The spread of infectious diseases between people must have three links-the source of infection, the route of transmission and the susceptible population. These three links are the biological basis for the occurrence and prevalence of infectious diseases in the population. Only when these three links exist at the same time can infectious diseases spread and spread, and as long as any one of them is cut off, infectious diseases cannot spread and spread. For example, vaccination is to protect susceptible people from infectious diseases.
First, the source of infection
Refers to an infected person or animal.
There must be pathogens living and reproducing in the source of infection, and they are excreted from time to time to infect others. Sources of infection include patients with infectious diseases, pathogen carriers (people with pathogens in their bodies but no clinical manifestations) and infected animals.
(1) Patients with infectious diseases are the main source of infection, and there are many pathogens in their bodies. The symptoms of patients are conducive to the spread of pathogens around the world. For example, pathogens can be excreted by coughing, sneezing, vomiting and diarrhea of patients. General infectious diseases, such as measles and viral hepatitis, are the most contagious at the initial stage. Some infectious diseases, such as diphtheria and typhoid, are contagious in the recovery period.
(2) A pathogen carrier refers to a person who carries a pathogen but has no disease symptoms. Pathogen carriers can be divided into three categories: latent carriers, post-illness carriers and "healthy" carriers. Because these pathogen carriers have no clinical symptoms and manifestations, they can constantly excrete pathogens, so they are not easy to be found and are the most important and dangerous source of infection.
(3) Infected animals Many infectious diseases come from animals (including domestic animals and wild animals), among which rodents are the most important because they can spread many diseases such as plague, hemorrhagic fever and leptospirosis. Diseases with animals as the source of infection are called "animal infectious diseases", such as anthrax, brucellosis, rabies, epidemic hemorrhagic fever and leptospirosis. These animal-borne infectious diseases can be transmitted from animals to people, but people generally do not infect each other (plague can spread from person to person).
Second, the route of transmission.
Transmission route refers to the way that pathogens are discharged from the source of infection and infected through certain routes. Infectious diseases are mainly spread through the following channels.
(1) Air transmission is the main transmission route of respiratory infectious diseases, including droplets and dust. Influenza, measles, diphtheria and other common diseases.
(2) Digestive tract transmission, also known as "fecal transmission" in medicine, is the same transmission route of digestive tract infectious diseases, including water and food transmission. Hands and flies are also important factors that pollute food. Common diseases such as dysentery, cholera, typhoid fever, hepatitis A, polio, etc. The temperature is high in summer and autumn, and pathogens such as bacteria and viruses are easy to grow and reproduce in water and food. Flies, cicadas and bedbugs are very active. Therefore, summer and autumn are the high incidence seasons of digestive tract infectious diseases.
(3) Contact transmission can be divided into direct contact and indirect contact. The former refers to infections caused by direct contact between pathogens and human skin mucosa, such as various skin infectious diseases, sexually transmitted diseases and rabies; The latter refers to the spread caused by contact with tableware and daily necessities contaminated by pathogens, such as hepatitis, diphtheria, trachoma, etc., and may also be spread through indirect contact.
(4) Insect-borne transmission refers to the mode of transmission through arthropods such as mosquitoes, flies, lice and fleas. Insect vector transmission can be divided into blood-sucking transmission and mechanical transmission. The former refers to arthropods that spread infectious diseases through blood sucking, such as mosquitoes that spread Japanese encephalitis and malaria through blood sucking, and fleas that spread plague through blood sucking; The latter means that arthropods mechanically carry and spread infectious diseases through their worms, claws and wings. For example, flies and cicadas generally do not suck blood, but spread germs to food and drinking water through their bodies, causing infectious diseases such as dysentery and typhoid fever.
(5) Other modes of transmission The modes of transmission of infectious diseases are quite complicated. In addition to the above, there are soil transmission (such as tetanus), blood transmission (such as hepatitis B) and placental transmission (such as rubella).
Third, susceptible people.
Susceptible population refers to people who lack resistance (specific immunity) to an infectious disease and are susceptible to infection. We usually inoculate all kinds of epidemic bacteria in order to improve the resistance of susceptible people and susceptible people to some (or some) infectious diseases.